Not specific to EST....

There's 2 new CID's....that do nothing.

2199
2200

If you look at the connector properties, you'll also see a couple additional fields that also do nothing (Specification and Facing).

I submitted to Support and they said they were for use w/Plant3d Content. I can't find any info on how that's done and considering I've heard that all the development teams for Plant3d were terminated in this winter's layoff and the product turned into an add-in for "AutoCAD One", I'm assuming the work was either never finished or if finished, never documented.